Port of Wilmington
BackgroundThe Port of Wilmington, an international seaport owned and operated by the North Carolina State Port Authority, is strategically located on the East Coast with easy access to national highways and rail networks. The port offers a 42-foot deep navigational channel for additional vessel capacity as well as includes state-of-the-art facilities, modern equipment and the latest cargo management technology. In the 2008 shipping season, the Port of Wilmington served 339 vessels carrying a 3.5 million tons of cargo. The port continues to invest in expanding to meet projected growth in international trade.
Project ScopeLocated on the Cape Fear River, about 30 miles from the open sea, saltwater had compromised the only decades old bulkhead. The steel seawall which supported an expansion area of the original port had corroded, leaving large cavities where the seawater washed-out the backfill. This caused the pavement above to sink into the formed cavities. The safe loading and unloading of containers or moving equipment through this area was compromised. Engineers designed a new cutoff wall to solve their issues. The port had learned their lesson with steel and would not consider it as a material option. Plans required a non-corrosive yet strong material; a steel alternative. Engineers looked for the strongest composite sheet piling available and choose to design with CMI’s UltraComposite sheet piling.
PerformanceThe engineer’s solution would need to support large equipment, vehicles and heavy containers in the day-to-day operations of the port. The design included a 1300 linear foot cut-off wall made of 30 foot long UltraComposite FRP sheets. UltraComposite products are corrosion-resistant and do not contain coal-tar epoxy, an environmental hazard that is often coated on steel structures. The UC 95 profile was chosen, as it is the strongest of all the offered FRP profiles. Most importantly, UltraComposite sheet piling is pultruded at an ISO certified manufacturing facility to ensure consistent high quality.
ConstructionPrior to installation, a mixture of asphalt and concrete was removed from the surface of the drive line. This open trench was along the back of the failing steel sheet pile bulkhead. Plans outlined the UC 95 to be driven behind the steel sheet pile wall to prevent water from rushing through the corroded holes and removing the supporting soil. The soils at the site were mostly sand. However, previous attempts at patching the corroded steel voids meant the driving area would also contain debris and other fill material. To install the sheet piling, crews used a 35 ton crawler crane with a 3500 lb vibrator hammer. A small crew of about 5 installed 70 to 80 feet a day of the 30 foot long 30 inch wide panels. They paired the panels during driving so that each driving episode achieved 5 linear feet of wall. A large cap was then fitted to the top of the cut-off wall connecting it to the existing structure. Then, concrete poured behind the wall. North Carolina Port Authority deemed the project a success and has since initiated and finished two additional phases of the UltraComposite cut-off wall.
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